The fire mission is for firing a battery of artillery targets at a map coordinate called in by your players. What you need to do to use it is:
1) Drop down some artillery on the map somewhere. They should be relatively close to one-another to get detected by the system.
2) Drop the 'Create Fire Mission' module near the units.
3) Choose the unit type from the drop-down. [If there are no units nearby an error message will be displayed instead]
4) Choose the number of guns from the battery, the number of rounds each gun should fire, and enter the map coordinates of the target. _this does not currently work with the 'Artillery Target' modules_
5) Choose 'OK' to have the units fire at the grid coordinate.

that is what iam doing but they're not fireing

I am having the same problem with it... Artillery does not fire whatsover. It tells the ETA and where it is firing on top, but that is it.

exactly that

Never mind, It is working again. Turned off some mods: Epoch, WSMaps, WSPatch, WSWeapons and Star Wars - Imperial Assault. Maybe some mods are interfering with Ares.

i dont have any onther mods installed.

Strange